Gas Sensors Research Articles

Ni-MoTe2 as a gas-sensitive material for sevoflurane exposure detection: A fluorinated anesthetic agent

Sevoflurane (C4H3F7O) is a fast-acting anesthetic with low side effects and is widely used in surgery for adults and children. However, small amounts of sevoflurane gas may leak from the breathing apparatus during surgery, which can pose a serious health risk to healthcare workers. In this regard, a study on monitoring of accidental leakage of sevoflurane by different gas-sensitive materials is carried out in this paper. The modified structures of Ni, Pt and Ag on the MoTe2 surface are built. The stabilities of Ni-MoTe2, Pt-MoTe2 and Ag-MoTe2 are investigated by adsorption configurations, Independent Gradient Model based on Hirshfeld partition (IGMH), Electronic Location Function (ELF) and Density of States (DOS). The adsorption properties of three gas-sensitive materials on sevoflurane are subsequently investigated. The gas-sensitive materials with excellent performance are selected combining sensitivity and recovery time. The results show that Ni and Pt can be stably doped on the surface of MoTe2 with forming chemical bonds. The adsorption of Ni-MoTe2 on sevoflurane is chemisorption with the adsorption energy of −0.811 eV. The DOS and IGMH results also indicate that the force of Ni-MoTe2 on sevoflurane is mainly the attraction caused by chemical bonding. Meanwhile, the sensitivity of Ni-MoTe2 for sevoflurane is between 56.26 % and 50.84 %, and the recovery time is between 35.21 s and 0.01157 s, which can meet the requirements of the gas sensor. As a result, Ni-MoTe2 can be used as a gas-sensitive sensor to detect the concentration of sevoflurane in the environment.

Research on Gas Recognition Based on Gas Sensor Array and Feature Analysis

Research on Gas Recognition Based on Gas Sensor Array and Feature Analysis

Feedback based gas sensing setup for ppb to ppm level sensing.

Sensing and quantification of gas at low concentrations is of paramount importance, especially with highly flammable and explosive gases such as hydrogen. Standard gas sensing setups have a limit of measuring ultra-low concentrations of few parts per billion unless the external gas cylinders are changed to ones with low concentrations. In this work, we describe a home-built resistance based gas sensing setup that can sense across a wide concentration range, from parts per billion to parts per million, accurately. This was achieved using two dilution chambers: a process chamber and a feedback assembly where a part of the output gas from the dilution chamber is fed back to the inlet mass flow controller, enabling enhanced dilutions without increasing the number of mass flow controllers. In addition, the gas-sensing setup can measure across a large temperature range of 77-900K. The developed setup was then calibrated using palladium thin films and ZnO nanoparticle thin films. The setup was tested for reproducibility, concentration response, temperature response, etc. Corresponding sensitivity values were calculated and found to be in good agreement with published values, validating our setup design.

Plasma-modified Co3O4 nanosheets for efficient CO detection: Insight into the structure-activity relationship

Exploring the correlation between crucial reactive sites and surface electron structure in the sensitive layer of gas sensors can achieve simultaneous optimization of kinetics and thermodynamics. In this work, Ar and O2 plasma sputtering are used to study how varying levels of Co3+ and oxygen vacancy affect the gas-sensitivity of Co3O4. The gas-sensing performance of Co3O4-O2PT (O2 plasma sputtering) is better than that of Co3O4-ArPT (Ar plasma sputtering), which exhibits a high response value (100 ppm-4.16) and quick response-recovery time (1.5 s/38 s). The enhancement of gas-sensing performance benefits from a high Co3+/Co2+ ratio, which provides strong CO-selective adsorption and oxidation capabilities. Therefore, the interfacial oxidation reaction reaches equilibrium rapidly. This work provides a straightforward and controllable modification approach and enhances the understanding of how oxygen vacancies and Co3+ affect Co3O4 gas sensors, which promotes the design and development of high-performance cobalt-based gas sensors.

Novel ordered dendritic InWO4-rGO p-n heterojunction for fast response to TEA

The ternary metal oxides that combine two different metal cations is an interesting candidate as sensing material based on their interesting properties. Hence, ordered dendrite InWO4 was successfully synthesized via a hydrothermal method, followed by the construction of an InWO4-rGO heterojunction to enhance detection capability for triethylamine (TEA) gas. The synthesized product underwent morphology and elemental composition analysis using various techniques. Gas sensing experiments revealed that the InWO4-rGO gas sensor, operating at the optimal temperature of 220 ℃, displayed a significantly improved response to 100 ppm TEA, with a high value of 59.5, in comparison to the pure InWO4 gas sensor (11.5 at 250 ℃). Additionally, the recovery time was reduced from 184 s to 122 s. Based on experimental data and gas sensing reaction theory, this study attributes the improved gas sensing performance to the formation of p-n heterojunction, a larger specific surface area and rGO's catalytic effect. This study not only introduces a novel addition to the gas sensing material family but also promotes the development of advanced gas sensors.

The alcohol lock built on carbon-based field-effect transistor sensor with Pd/ZnO floating gate structure used for drunk driving surveillance

The ignition interlock device, an onboard alcohol detection system for supervising cases of driving under the influence (DUI), is crucial for ensuring traffic safety. As a key component of this system, ethanol sensor faces challenges like integration difficulties and poor anti-humidity property, limiting its potential applications. Herein, from the perspective of miniaturization and integration, a carbon-based field effect transistor (FET) gas sensor with a floating-gate (FG) structure is proposed for fast ethanol detection in exhaled breath. The proposed sensing FG structure enables the traditional FET to acquire the perceptibility toward target gas, and the FET with excellent amplification ability further enhances the gas-sensing response. The detection range of the sensor is 0–600 ppm, with a response deviation of merely 11 % toward 50 ppm ethanol within a humidity range of 10 %-90 % relative humidity (RH). Additionally, benefited from the good consistency of the semiconductor technology, relative standard deviation (RSD) of the responses from different batches is 2.1 %, confirming its potential for mass production. The tiny size (1.5 mm×1.5 mm) of the sensor and the compatible fabrication process with MEMS process are conducive to the on-chip integration. This work provides a boost to the process of advancing the research and development of automotive alcohol locks, and facilitate their popularization.

Novel β-CdSnO3-SnO2 nanorod-like heterostructure materials for enhancing n-butanol sensing

n-butanol detection is crucial to environmental protection and mankind’s health because of its toxicity and irritation to the respiratory system. Mono-metal oxide semiconductors (such as SnO2) often face disadvantages such as low sensitivity, insufficient selectivity, and a high detection limit. Constructing heterojunctions has been considered an efficient way to enhance the performance of MOS gas sensors. This work presents the synthesis of a series of β-CdSnO3-SnO2 nanorod-like heterostructures with good n-butanol sensitivity using a hydrothermal and post-calcination approach. The optimized CSO/SO-8 shows the highest response value about 90–100 ppm n-butanol at 190 °C, which is 15 times greater than that of SnO2, and 6.5 times more than that of β-CdSnO3. Meanwhile, the CSO/SO-8 also exhibits a short response and recovery time (1–2 s/63 s). More importantly, the detection limit is reduced to ppb level (50 ppb). The improved gas-sensitive properties can be explained by the formation of n-n heterojunctions between β-CdSnO3 and SnO2, which increases the content of chemisorbed oxygen, thus enhancing the performance of the gas-sensitive. Our work not only provides a material with n-n heterostructures but also the strategy for constructing heterojunctions to improve gas-sensitive properties.

Biotemplate synthesis of SnO2 hollow porous structures for enhanced isopropanol sensing performance

Researchers are showing significant interest in the development of nanostructures with hierarchical porosity. This study introduces an eco-friendly, cost-effective, and straightforward method to create SnO2 hollow porous nanostructures using the peony as a biotemplate. A comprehensive analysis of the gas sensing characteristics of these hierarchical SnO2 hollow porous nanostructures is conducted. The results show that the gas sensor based on SnO2 showcases relatively high response values measuring 18.3 and exhibits rapid response speed of 1 s to 100 ppm isopropanol, even at a comparably low operating temperature of 180 °C. Additionally, the sensor displays good repeatability and long-term stability, which can be attributed to the inherent advantages stemming from its distinct structure. Therefore, this study provides experimental and theoretical foundations for the potential application of hollow porous SnO2 structures in sensor technology.

Machine Learning‐Assisted Research and Development of Chemiresistive Gas Sensors

Machine Learning‐Assisted Research and Development of Chemiresistive Gas Sensors

Inverted Pyramidal Porous Silicon by Chemical Etching and PECVD Rebuilding for Selective Gas Sensing

Inverted Pyramidal Porous Silicon by Chemical Etching and PECVD Rebuilding for Selective Gas Sensing

Design and sensitivity study of a novel Z-shaped gate TFET sensor with SiGe source for chemical analyte detection

In this work, we have designed a chemical gas sensor using a Z-shaped gate tunnel FET with a SiGe source. Here, the gate material is a conducting organic polymer, which allows for the effective detection of a variety of chemical analytes. Over the course of the sensitivity investigation, several chemical analytes were exposed, including hexane, methanol, iso-propanol, and chloroform. Detecting chemical gases is feasible due to the work-function modification of the conducting polymer with exposure to the chemical gas vapors. This leads to modifications in the electrical properties of the suggested gas sensor, which serves as a sensing metric. The impact of surrounding temperature on various sensitivity parameters of the TFET-based gas sensor is also investigated. The proposed heterostructure Z-TFET (ZHS-TFET) offers a peak drain current sensitivity of 5.65 × 105 in the case of chloroform, which is four times higher than the sensitivity provided by the ZTFET sensor. Further, the suggested chemical sensor offers a higher subthreshold swing sensitivity (SSS) of 0.29 and a current ratio sensitivity (Sratio) of 3.18. As a result of its higher-sensitivity nature and improved electrostatic performance, the proposed sensor with conducting polymer as the gate metal may be able to meet the needs of the chemical and pharmaceutical industries, as well as environmental monitoring and biological diagnostics.

Synergy of active sites and charge transfer in (WO3/phosphotungstic acid)@MoS2 hierarchical heterostructures for highly sensitive and selective ppb-level NO2 sensing

In this paper, (WO3/phosphotungstic acid)@MoS2 core-shell hierarchical nanofibers were fabricated by coaxial electrospinning technology to construct a high-performance gas sensing material combining the synergy of active sites and charge transfer. Polyoxometalate (POMs), as electrons acceptor, can separate electrons and holes, and thus promote sensing performances. Under optimized test conditions, the WO3/PW12@MoS2 sensor exhibited sensitive response of 3.4 to 2 ppm NO2 gas. That is obviously enhanced than WO3@MoS2 sensor, and much higher than that of 100 ppm other interference gases, indicating a satisfactory selectivity. Repeatability, long-term stability and humidity resistance were systematically investigated. The heterojunctions formed between the three components can extend electron lifetime, while allowing more electrons to migrate towards the surface to react with oxygen molecules in the air, thus promote the gas response. This work provides meaningful information for the practical application of POMs in gas sensors.

ZnO nanowires decorated with Pt nanoclusters for selective detection of ppb-level nitrogen dioxide

Noble metal loading is an efficient way to improve the sensing performance of metal oxide semiconductor (MOS) gas sensors. In this work, platinum (Pt) nanoclusters loaded ZnO nanowires (Ptc-ZnO) were used to fabricate a NO2 sensor. Pure ZnO nanowires were prepared by a solvothermal method and Pt nanoclusters were loaded via a sacrificial templating route. The Ptc-ZnO based sensor with a trace of Pt loading (0.17 wt%) shows a high response to ppb-level NO2 (26.1–100 ppb), 4.4 times higher than that of pure ZnO. Additionally, it also exhibits excellent selectivity, low theoretical limit of detection (1.19 ppb) and good stability to humidity. The enhancing mechanism on gas sensing performance by Pt loading was discussed and investigated via HAADF-STEM, XPS, NO2-TPD and other methods. This work provides a way to develop gas sensor for ultralow NO2 concentration real-time detection.

DFT study of gas responses to CH4, H2S, and CO on TM Atom (Sc, V, Cr, Mn)-modified HfSe2 monolayers

In this study, the adsorption of waste gases (CH4, H2S, CO) generated during the extraction, processing, and utilization of natural gas on TM atom (Sc, V, Cr, Mn)-modified HfSe2​ surfaces were analyzed using Density Functional Theory (DFT) calculations. Initially, the doping effects of the four TM atoms were examined, followed by a detailed investigation of the adsorption of these three gases in terms of adsorption energy, band structure, density of states (DOS), charge transfer, and recovery time. Among the TM atoms, Sc doping was found to be the most favorable due to its highest adsorption energy. However, in subsequent gas adsorption processes, it was observed that V and Mn-modified HfSe2 surfaces exhibited better adsorption performance for H2S and CO. Furthermore, it was discovered that at high temperatures, V-HfSe2 can function as a gas sensor for CO, while at room temperature, V-HfSe2 and Mn-HfSe2 can serve as high-precision real-time monitoring sensors for H2S and CO, respectively.

Novel development of laser synthesized double orthogonal PSi surface NH3 gas sensors

Novel development of laser synthesized double orthogonal PSi surface NH3 gas sensors

Metal-Organic Framework-Derived Au-Doped In2O3 Nanotubes for Monitoring CO at the ppb Level.

Achieving selective detection of ppb-level CO is important for air quality testing at industrial sites to ensure personal safety. Noble metal doping enhances charge transfer, which in turn reduces the detection limit of metal oxide gas sensors. In this work, metal-organic framework-derived Au-doped In2O3 nanotubes with high electrical conductivity are synthesized by pyrolysis of the Au-doped metal-organic framework (In-MIL-68) as a template. Gas-sensing experiments reveal that the detection limit of 0.2% Au-doped In2O3 nanotubes (0.2% Au, mass fraction) is as low as 750 ppb. Meanwhile, the sensing material shows a response value of 18.2 to 50 ppm of CO at 240 °C, which is about 2.8 times higher than that of pure In2O3. Meanwhile, the response and recovery times are short (37 s/86 s). The gas-sensing mechanism of CO is uncovered by in situ DRIFTS through the reaction intermediates. In addition, first-principles calculations suggest that Au doping of In2O3 significantly enhances its adsorption energy for CO and improves the electron transfer properties. This study reveals a novel synthesis pathway for Au-doped In2O3 nanotubular structures and their potential application in low concentration CO detection.

Covalent surface modification of single-layer graphene-like BC6N nanosheets with reactive nitrenes for selective ammonia sensing via DFT modeling

Novel graphene-like nanomaterials with a non-zero bandgap are important for the design of gas sensors. The selectivity toward specific targets can be tuned by introducing appropriate functional groups on their surfaces. In this study, we use first-principles simulations, in the form of density functional theory (DFT), to investigate the covalent functionalization of a single-layer graphitized BC6N with azides to yield aziridine-functionalized adducts and explore their possible use to realize ammonia sensors. First, we determine the most favorable sites for physical adsorption and chemical reaction of methylnitrene, arising from the decomposition of methylazide, onto a BC6N monolayer. Then, we examine the thermodynamics of the [1 + 2]–cycloaddition reaction of various phenylnitrenes and perfluorinated phenylnitrenes para-substituted with (R = CO2H, SO3H) groups, demonstrating favorable energetics. We also monitor the effect of the functionalization on the electronic properties of the nanosheets via density of states and band structure analyses. Finally, we test four dBC6N to gBC6N substrates in the sensing of ammonia. We show that, thanks to their hydrogen bonding capabilities, the functionalized BC6N can selectively detect ammonia, with interaction energies varying from −0.54 eV to −1.37 eV, even in presence of competing gas such as CO2 and H2O, as also confirmed by analyzing the change in the electronic properties and the values of recovery times near ambient temperature. Importantly, we model the conductance of a selected substrate alone and in presence of NH3 to determine its effect on the integrated current, showing that humidity and coverage conditions should be properly tuned to use HO2C-functionalized BC6N-based nanomaterials to develop selective gas sensors for ammonia.

The synergistic effect of Cd-doped and S-vacancies in CdxZn1-xIn2S4 2D nanosheets for high-performance triethylamine sensing

Ternary metal sulfides with suitable band gaps, high physicochemical stability, and unique two-dimensional (2D) nanostructures are expected to be the next-generation high-performance gas sensors following the MOS type. Doping engineering is utilized as an effective strategy to improve the semiconductor surface activity and enhance its gas-sensitive properties. In this paper, the energy band structure and surface chemical oxygen of ZnIn2S4 (ZIS) materials was tuned by selectively introducing substitutional Cd to replace the Zn sites in ZIS crystals. Meanwhile, the introduction of Cd-ions brings more abundant S vacancy defects, enhances the acid-base interactions at the interface, and pushes the extent of surface redox reactions. In addition, by combining the strong adsorption of ZIS to triethylamine, the CdxZn1-xIn2S4 nanosheets achieved highly improved sensing properties, including better response (63.38–100 ppm), enhanced selectivity (STEA/sother = 12.9), and accelerated response/recovery (4 s/32 s). The results confirm the feasibility of developing low-cost, high-performance 2D metal sulfide gas sensing materials through rational structural design and optimization.

Atomic-Level Insights of Polypyrrole Grafted InGaZnO Structure for ppb-Level Ozone Gas Sensing at Low Operating Temperature.

This study explores the utilization of the organic conductive molecule Polypyrrole (PPy) for the modification of Indium Gallium Zinc Oxide (IGZO) nanoparticles, aiming to develop highly sensitive ozone sensors. Pyrrole (Py) molecules undergo polymerization, resulting in the formation of extended chains of PPy that graft onto the surface of IGZO nanoparticles. This interaction effectively diminishes oxygen vacancies on the IGZO surface, thereby promoting the crystallization of the IGZO (1114) facets. The resultant structure exhibits promising potential for achieving high-performance wideband semiconductor gas sensors. The IGZO/PPy device forms a Straddling Gap heterojunction, facilitating enhanced electron transfer between IGZO and ozone molecules. Notably, the adsorption and desorption of ozone gas occur efficiently at a low temperature of approximately 25 °C, obviating the need for additional energy typically associated with wide bandgap semiconductor materials. Density Functional Theory (DFT) calculations attribute this efficiency to the enhanced number of active sites for ozone adsorption, facilitated by hydrogen bonds. The substantial conductivity of PPy, combined with its planar ring structure, induces positively charged polarization on the IGZO side upon ozone adsorption. The resultant device exhibits exceptional sensitivity, boasting a 4-fold improvement compared to sensors reliant solely on IGZO. Additionally, the response time is significantly reduced by a factor of 10, underscoring the practical viability and enhanced performance of the IGZO/PPy sensor field.

Unraveling the Chicken Meat Volatilome with Nanostructured Sensors: Impact of Live and Dehydrated Insect Larvae Feeding.

Incorporating insect meals into poultry diets has emerged as a sustainable alternative to conventional feed sources, offering nutritional, welfare benefits, and environmental advantages. This study aims to monitor and compare volatile compounds emitted from raw poultry carcasses and subsequently from cooked chicken pieces from animals fed with different diets, including the utilization of insect-based feed ingredients. Alongside the use of traditional analytical techniques, like solid-phase microextraction combined with gas chromatography-mass spectrometry (SPME-GC-MS), to explore the changes in VOC emissions, we investigate the potential of S3+ technology. This small device, which uses an array of six metal oxide semiconductor gas sensors (MOXs), can differentiate poultry products based on their volatile profiles. By testing MOX sensors in this context, we can develop a portable, cheap, rapid, non-invasive, and non-destructive method for assessing food quality and safety. Indeed, understanding changes in volatile compounds is crucial to assessing control measures in poultry production along the entire supply chain, from the field to the fork. Linear discriminant analysis (LDA) was applied using MOX sensor readings as predictor variables and different gas classes as target variables, successfully discriminating the various samples based on their total volatile profiles. By optimizing feed composition and monitoring volatile compounds, poultry producers can enhance both the sustainability and safety of poultry production systems, contributing to a more efficient and environmentally friendly poultry industry.